[Open-scap] Phasing out the RHEL6 CI

[Matěj Týč]

Dear community,

the possibility to build the OpenSCAP "oscap" suite on RHEL6 using those 
dated utilities s.a. python2.6 is becoming a luxury. Sometimes, passing 
the CI for RHEL6 requires some weird workarounds that take time to 
design and implement and those workarounds just complicate the code, 
they don't bring benefits.

As RHEL6 won't get any significant updates, the ability to compile 
recent versions of the scanner suite on RHEL6 seems irrelevant. Do you, 
our precious community around the project, have arguments why the RHEL6 
should be part of the CI?

If there are no agreed-upon reasons to do otherwise, we are leaning 
towards switching the RHEL6 CI off within two weeks, i.e. in the first 
half of March.

On behalf of the Brno Security Compliance team,
Matěj Týč